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<br />razorback sucker larvae have been successfully reared on selected, dry commercial <br />diets (Tyus and Severson 1990, Severson et. al. 1991). <br />AQe and Growth <br />Estimates of growth rates for individuals captured in the wild have been hampered b <br />Y <br />difficulties in determining age. McCarthy and Minckley (1987) evaluated seven <br />different morphological structures, and determined that only otoliths gave reliable ages. <br />Their results indicated that razorback suckers are Ion -lived fish: individuals fr <br />g om Lake <br />Mohave were 24 to 44 years of age in the 1980s (McCarthy and Minckley 1987). <br /> <br />Razorback suckers grow rapidly.during the first six years, but growth is very slow for <br />older individuals in extant populations (McCarthy and Mincldey 1987, Minckley et al. <br />1991). Adults in the Lake Mohave population have shown little or no growth fora <br />period of at least 20 years (Minckley et al. 1991). Tyus (1988) found slow growth <br />(average of 2.2 mmtyear) for 39 adult razorback suckers recaptured 1-8 years after <br />tagging, and Modde et al. (1996) reported similar results. Adults from the San Juan <br />River recaptured one year after tagging had grown an average 3.1 mm (Roberts and <br />M <br />oretti 1989). <br /> <br />Most of the information on the growth of early life stages is from hatchery-produced <br />fish, or fish spawned in human-influenced environments. Growth under these <br />controlled conditions may reflect potential rates rather than the rates that might occur in <br />22 <br /> <br />